Add tests
support for multiplexing log streaming in api v1.6

http://docs.docker.io/en/latest/api/docker_remote_api_v1.6/#attach-to-a-container
added tests and fixed multiplexing log streaming.
testing: sending prefix header on attach.
testing: using utils.NewStdWriter.
image: remove self-assignment.
installing lvm on ci.
travis: fixed typo.
travis: using pushd/popd instead cd.
docker: using docker.Ports instead docker.PortMapping.
Merge branch 'copy_from_container' of github.com:gemnasium/go-dockerclient
container/copy: improve test coverage
container: minor tweaks to docs
example: fix function name
readme: add godoc badge
Add CopyFromContainer example
Godeps: declare file
travis: use godep to run tests
travis: build against go 1.1.2 and go 1.2

Also test 386 and amd64.
travis: call godep restore before running tests